Vehicular head-up display apparatuses are used to reflect light transmitted through a display panel of a projection unit to a semi-transmissive plate such as a windshield of a vehicle. The reflected light causes an operator of the vehicle to recognize a virtual image of a display surface of the display panel.
The operator of the vehicle visually recognizes the virtual image of the display surface from the front direction of the display surface. The vehicular head-up display apparatus is such that the luminance in the front direction of the display surface is higher than that in an oblique direction. In order to increase the luminance in the front direction of the display panel, the vehicular head-up display apparatus may include a diffusion plate which is high in total light transmittance and parallel light transmittance. However, in the vehicular head-up display apparatus, as the parallel light transmittance increases, unevenness tends to occur in the luminance in the front direction of the display surface.